(Brachiopoda, Strophomenida) from the Silurian of Gotland, Sweden
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Pala¨ontol Z (2011) 85:201–229 DOI 10.1007/s12542-010-0088-3 RESEARCH PAPER Strophomenidae, Leptostrophiidae, Strophodontidae and Shaleriidae (Brachiopoda, Strophomenida) from the Silurian of Gotland, Sweden Ole A. Hoel Received: 23 September 2010 / Accepted: 1 October 2010 / Published online: 13 November 2010 Ó The Author(s) 2010. This article is published with open access at Springerlink.com Abstract Twelve species of Brachiopods are described short ranged and occurs in low-energy environments in the from the Silurian of Gotland, six furcitellinines and six latest Llandovery. The species belonging to the Stroph- ‘‘strophodontids.’’ One is new—Strophodonta hoburgensis odontidae (Strophodonta hoburgensis n. sp.) and Shalerii- n. sp. The furcitellinines are moderately common and dae [Shaleria (Janiomya) ornatella and S. (Shaleriella) diverse in the lower part of the succession, but the last ezerensis] occur only in high-energy environments and have species disappears in the middle Hemse beds (*middle a short range within the late Ludlow. Ludlow). Three genera are represented: Bellimurina, Pentlandina and Katastrophomena, with the species and Keywords Silurian Á Llandovery Á Wenlock Á Ludlow Á subspecies B. wisgoriensis, P. tartana, P. loveni, P. lewisii Strophomenide Á Furcitellininae Á Leptostrophiidae Á lewisii, K. penkillensis and K. antiquata scabrosa. Most of Strophodontidae Á Shaleriidae the taxa are confined to low energy environments, but P. loveni was evidently specialized for the high energy reef Kurzfassung Zwo¨lf arten Brachiopoden von der Silurium environments of the Ho¨gklint Formation. B. wisgoriensis Gotlands sind beschrieben. Sechs Furcitellininen und sechs displays environmentally induced morphological variability ,,Strophodonten‘‘. Eine Gattung ist neu; Strophodonta in developing strong, frilly growth lamellae in high-energy hoburgensis sp. n. Der Unterfamilie Furcitellininae sind auf environments. The ‘‘strophodontids,’’ although belonging Gotland ein gema¨ßigt ha¨ufiger und gering diverser to three different families, share a common morphology Bestandteil der untere teil der Abfolgen, aber die letzte Art consisting of denticles along the hinge line, a semi-circular der Unterfamilie verschwindet in den mittleren Hemse outline, unequally to finely costellate ornament and, most Schichten des mittleren Ludloviums. Die drei Gattungen importantly, a concavo-convex profile with both valves of Bellimurina, Pentlandina und Katastrophomena sind mit the same curvature, enclosing a very small body chamber. den folgenden Arten und Unterarten vertreten: B. wisgori- Two leptostrophiids are generalists, occurring in both high- ensis, P. tartana, P. loveni, P. lewisii lewisii, K. penkillensis and low-energy environments and with long stratigraphical und K. antiquata scabrosa. Die meisten Taxa sind auf ein ranges [Mesoleptostrophia filosa; latest Llandovery through niedrigenergetisches Ablagerungsmilieu beschra¨nkt, wohi- the entire Ludlow. Brachyprion (Brachyprion) semiglob- ngegen P. loveni offensichtlich auf das hochenergetische osa; latest Llandovery to latest Wenlock]. The third lep- Milieu im Bereich der Riffe der Ho¨gklint Formation spez- tostrophiid (Brachyprion (Erinostrophia) walmstedti)is ialisiert war. B. wisgoriensis weist eine milieuabha¨ngige, morphologische Variabilita¨t auf, die sich in der Entwicklung von ru¨schenartigen Wachstumslamellen unter hochenerge- O. A. Hoel Department of Earth Sciences (Palaeobiology Program), tischen Bedingungen auszeichnet. Die ,,Strophodonten‘‘, Uppsala University, Norbyva¨gen 22, 752 36 Uppsala, Sweden ho¨rt zu drei verschiedene Familien zu. Sie teilen eine gem- einsame morphologie die von der volgende bestehen: kleine Present Address: za¨hne la¨ngs die linie des Ha¨nges, eine semi sirkulares O. A. Hoel (&) Herumveien 35, 1430 A˚ S, Norway Umriss, ungleichartiger zu feiner costellate Skulptur, e-mail: [email protected] und am wichtigsten, eine konkavo-konvexes profil mit 123 202 O. A. Hoel beiden Schalen mit gleichartig Kurve, der eine sehr divided two of the species into several subspecies, although kleine Ko¨rperkammer umschliesst. Zwei Leptostrophiiden making clear that he considered most of the morphological (Mesoleptostrophia filosa und Brachyprion (Brachyprion) variation to reflect micro-environmental rather than genetic semiglobosa) sind generalisten, die im sowohl Hochenergie- causes. als Swachenergiemilieuen und durch langer stratigraphisher Members of this subfamily are relatively rare in the Intervall auftreten. Der dritten Leptostrophiid (Brachyprion Wenlock faunas of the British Isles, and this also is the case (Erinostrophia) walmstedti) hat eine ku¨rtzere stratigrafisher on Gotland. The collections in the Swedish Museum of Auftreten und tret im Swachenergiemilieuen in die spa¨testen Natural History, Stockholm, and Museum of Evolution, Llandovery auf. Die die zu den Strophodontidae (Stroph- Uppsala, contain only about 300 specimens of furcitelli- odonta hoburgensis sp.n.) und Shaleriidae (Shaleria (Jani- nines, in contrast to over 1,000 specimens of leptaenines omya) ornatella und S.(Shaleriella) ezerensis) zuho¨rt treten (Hoel 2005). The furcitellinines also have a more restricted nur im Hochenergiemilieuen auf und treten durch eine distribution than the leptaenines; Pentlandina and Belli- ku¨rzere Interwall innerhalb der spa¨tere Ludlow auf. murina occur only along the NW coast and on Stora Karlso¨, while Katastrophomena has a similar restricted Schlu¨sselwo¨rter Silurium Llandovery Á Wenlock Á distribution in the lower part of the succession. In the Ludlow Á Furcitellininae Á Leptostrophiidae Á Ludlow Hemse group, specimens are also found further Strophodontidae Á Shaleriidae Á Schweden east, but they are mainly confined to low-energy environ- ments within the western marlstone area. The geographical distribution of furcitellinine species is shown in Fig. 1, Introduction which also shows the distribution of the main facies. The stratigraphical ranges are shown in Fig. 2. The strophomenide taxa found in the Silurian succession of While the closely related furcitellinines can be mor- Gotland, Sweden, are a mix of groups that are typical of the phologically extremely variable both within and between Ordovician and groups that are characteristic of the species, several other strophomenide taxa occur in the Devonian faunas. Representative taxa of the former are the Gotland succession that belong to three different families, Strophomenidae and Leptostrophiidae, while the latter yet share a very similar morphology: This similarity con- belong to the Strophodontidae and the Shaleriidae. Some of sists of a semicircular shell shape, concavo-convex profile the species described in this article have been relatively with very narrow body cavity (the opposing valves lie very well described and figured elsewhere, mainly from the close to each other along the entire length of the animal), a British Isles, but apart from the rather cursory papers of fairly similar unequally parvicostellate radial ornament Lindstro¨m(1861) and Bassett and Cocks (1974), very few (considered to be primitive by Harper and Boucot 1978c, illustrations of Gotland material have been published. The p. 6), usually without any rugation, and development of lack of illustrations is somewhat surprising, with respect to denticles for articulation along the hinge. On Gotland, the classical status of the area, and the large amount of species of Brachyprion and Mesoleptostrophia are among papers dealing with the island’s geology. During this work, the most common and widespread brachiopod taxa. Both it was recognized that many species display quite extensive genera occur in high- and low-energy environments with- variation in morphology. I have therefore decided to out displaying much phenotypical variation attributable to illustrate each species with a larger number of illustrations environmental influences. On the other hand, the other two than has previously been usual. Hopefully this makes the fairly similar genera described here (Strophodonta and paper more useful for later studies both of the animals’ Shaleria) have a short temporal range on Gotland and are palaeobiogeography and their palaeobiology. only found in high-energy, shallow water environments. The Strophomenidae are a predominantly Ordovician group, but a few members of the subfamily Furcitellinae cross the Ordovician-Silurian boundary, and a single genus Geological setting (Katastrophomena) persists into the Ludlow (Cocks and Rong 2000). The Llandovery furcitellinine taxa of the The island of Gotland in the Baltic Sea, east of the Swedish British Isles were studied by Cocks (1968), who described mainland, forms a small, exposed part of the much larger nine nominal species and a few specimens under open area of Palaeozoic rocks comprising the bedrock of the nomenclature, belonging to six genera. From the Wenlock southern-central region of the Baltic Sea, the East Baltic of the Welsh Borderland and South Wales, Bassett (1974) states and parts of Russia and Belarus. The Silurian suc- described three furcitellinine species belonging to the cession on Gotland spans a time interval from the latest genera Pentlandina and Katastrophomena. He also noted Llandovery to the late Ludlow. During that time Gotland that the variation within each species was considerable, and was situated near the southern margin of Baltica, about 158 123 Strophomenidae, Leptostrophiidae, Strophodontidae and Shaleriidae (Brachiopoda, Strophomenida) 203 Fig. 1 Map of Gotland showing